The probe is one of several at the federal, state and congressional level aimed at determining if the companies use their considerable clout in the online market illegally to hurt rivals or otherwise break competition law.

“We have received initial submissions from Alphabet, Amazon, Apple and Facebook as part of our investigation. While we do not yet have all of the information we requested, we expect that all four companies will provide the information in short order,” the committee’s leaders said in a joint statement.

“We look forward to their continued compliance with the committee’s investigation,” they said in the statement.

The statement was from Representatives Jerrold Nadler, chairman of the Judiciary Committee; Doug Collins, the top Republican on the committee; David Cicilline, chair of the antitrust subcommittee and Jim Sensenbrenner, the top Republican on the antitrust subcommittee.

“We will hold additional hearings, discussions and round tables as our investigation continues,” the statement said.

Facebook Inc and Google declined to comment, while Amazon.com Inc and Apple Inc did not immediately respond to a request for comment.